1. Field of the Invention
The present invention relates to a lens sheet and a liquid crystal display panel, which are used in a display device capable of displaying different images for a plurality of view points.
2. Description of the Related Art
Recently, there have been actively conducted developments for making it possible to display different images for a plurality of view points with a liquid crystal display device. For example, there have been disclosed a display device which simultaneously provides different images for a plurality of observers located in different directions as depicted in Japanese Unexamined Patent Publication H06-332354 (Paragraphs 0070-0073, FIG. 10: Patent Document 1), or a stereoscopic image display device as depicted in Japanese Unexamined Patent Publication 2005-208567 (Paragraphs 0009-0012, FIG. 41: Patent Document 2).
Both of the display devices disclosed in Patent Documents are characterized to use a lenticular lens that is formed with cylindrical lenses, and to display a plurality of images by distributing those to arbitrary different directions.
FIG. 26 shows a sectional view of a widely-used liquid crystal display panel with a plurality of view points, which uses a lenticular lens sheet.
A thin film transistor substrate (referred to as a TFT substrate) 301 and a color filter substrate (referred to as a CF substrate) 305 are laminated via a seal member 309, and liquid crystal 308 is sealed between the both substrates 301 and 305.
On a flat surface opposing to the CF substrate 305, the TFT substrate 301 includes: a thin film element region 302 on which a TFT pixel switch array, signal lines, scanning lines, pixel electrodes, a TFT driving circuit, and the like are formed; and an alignment film 304 to which rubbing processing is applied. Further, on a flat surface on the opposite side of that flat surface, the TFT substrate 301 includes a polarization plate 303.
In the meantime, on a flat surface opposing to the TFT substrate 301, the CF substrate 305 includes: a counter electrode forming layer 306 on which counter electrodes, a metal shielding film, and the like are formed; a color filter layer (referred to as a CF layer hereinafter) 307 formed with a color layer, a black matrix, an overcoat layer, and the like; and an alignment film 304 to which rubbing processing is applied. Further, on a flat surface on the opposite side of that flat surface, the CF substrate 305 includes a polarization plate 303 and a lenticular lens sheet 310.
Furthermore, a backlight module, a driving IC, a flexible print cable (referred to as FPC hereinafter), and the like are mounted, thereby completing a liquid crystal display device.
In general, the lenticular lens sheet 310 is manufactured by molding resin, glass, or the like by using a mold as disclosed in Japanese Unexamined Patent Publication 2004-280087 (Paragraph 0062: Patent Document 5) and Japanese Unexamined Patent Publication 2008-203430 (Paragraph 0025: Patent Document 6) or manufactured by using a nip roll as disclosed in Japanese Unexamined Patent Publication 2000-292858 (Paragraphs 0020-0022: Patent Document 7). In the meantime, Patent Document 3 and Patent Document 4 disclose lens sheets that can be manufactured in stable measurements at a low cost without using a mold or the like.
As shown in FIG. 27, in the widely-used lenticular lens sheet, lens-forming linear protrusions 312 and lenses 313 are provided on a substrate 311. Resin, glass, or the like is used for the substrate 311, resin is used for the linear protrusions 311, and ultraviolet curing resin, thermosetting resin, or the like is used for the lenses 313. In some cases, a liquid-repellent function depicted in WO95/09372 Publication (pp. 21-25, FIG. 8: Patent Document 3), a light-shielding function depicted in Japanese Unexamined Patent Publication H7-281181 (Paragraphs 0044-0052, FIG. 1: Patent Document 4), and the like are given to the linear protrusions 312.
However, there is normally an issue of having contraction in the ultraviolet curing resin, the thermosetting resin, and the like used for forming the lens.
The length in the major axis direction (extending direction) of each lens in the lenticular lens sheet is equivalent to the longitudinal length of a screen size of display device. Thus, when the screen size is formed in a large scale, influences of the contraction of the resin cannot be ignored. In particular, liquid crystal display devices have been continuously expanded from year to year, and liquid crystal display devices of 100 inches or more at the most have now been developed.
In the meantime, the length of the minor axis direction (pitch direction) of the lens is determined in accordance with the size of pixels in the liquid crystal display devices, so that it does not depend so much on the size of the screen.
As a result, the aspect ratio of the lens tends to be increased in accordance with the expansion of the size of the screen. In general, contraction of the resin depends largely on the shape. Thus, the anisotropy of the contraction appears greatly when the aspect ratio becomes larger, so that the stableness in the measurements tends to be deteriorated.